Elevation of Cleaved p18 Bax Levels Associated with the Kinetics of Neuronal Cell Death during Japanese Encephalitis Virus Infection

Abstract

Japanese encephalitis virus (JEV) infection induces uncontrolled neuronal apoptosis, leading to irreversible brain damage. However, the mechanism of JEV-induced neuronal apoptosis has not been clearly elucidated. This study aimed to investigate both virus replication and neuronal cell apoptosis during JEV infection in human neuroblastoma SH-SY5Y cells. As a result, the kinetic productions of new viral progeny were time- and dose-dependent. The stimulation of SH-SY5Y cell apoptosis was dependent on the multiplicity of infections (MOIs) and infection periods, particularly during the late period of infection. Interestingly, we observed that of full-length Bax (p21 Bax) level started to decrease, which corresponded to the increased level of its cleaved form (p18 Bax). The formation of p18 Bax resulting in cytochrome c release into the cytosol appeared to correlate with JEV-induced apoptotic cell death together with the activation of caspase-3/7 activity, especially during the late stage of a robust viral infection. Therefore, our results suggest another possible mechanism of JEV-induced apoptotic cell death via the induction of the proteolysis of endogenous p21 Bax to generate p18 Bax. This finding could be a new avenue to facilitate novel drug discovery for the further development of therapeutic treatments that could relieve neuronal damage from JEV infection.

Pathogenicity and virulence of Japanese encephalitis virus: Neuroinflammation and neuronal cell damage

“…Furthermore, the involvement of mitochondrion-dependent pathways in regulating JEV-induced neuronal apoptosis has also been elucidated. Infection of cultured neuronal cells caused the JEV NS2B-NS3 protease-induced or p21-Bax/p18-Bax-mediated release of mitochondrial cytochrome C in the cytoplasm, indispensable for the activation of caspase-3/7-mediated apoptosis pathways in these cells [ 54 , 55 ]. Alternatively, the production of ROS and the stimulation of ASK1/ERK1/p38-MAPK pathway in infected cells is also linked to the NS4B-NS3-induced mitochondrion-dependent apoptosis [ 54 , 56 ].…”

Duck Tembusu virus induces stronger cellular responses than Japanese encephalitis virus in primary duck neurons and fibroblasts

“…A previous study demonstrated that JEV induced apoptosis in SH-SY5Y cells via the activation of the caspase-3/7 pathway in a time-dependent manner. 26 Similarly, we found that DTMUV KPS54A61 and JEV JaGAr-01 could induce apoptosis in DN and CCL-141 probably via the caspase-3dependent pathways (Figures 3b-e, 4, 5). However, higher numbers of DN and CCL-141 cells infected with DTMUV KPS54A61 underwent apoptosis compared with cells infected with JEV JaGAr-01 (Figure 3d,e).…”

“…[21][22][23][24] It is known that JEV infects various mammalian neuronal cell types and causes neuronal death. [25][26][27] However, the pathogenesis of JEV infection in birds including viral neurotropism and innate immune response has not been investigated.…”

Role of apoptosis in Duck Tembusu virus infection of duckling brains in vivo

“…The flaviviruses infection is capable of triggering multiple apoptotic pathways, such as mitochondria-dependence ( Suzuki et al., 2018 ), death receptor ( Liao et al., 2010 ), and endoplasmic reticulum ( ER ) stress ( Huang et al., 2016 ; Turpin et al., 2021 ). JEV triggered apoptosis of N18 (a mouse neuroblastoma cell line) cells through the mitochondrial pathway ( Tsao et al., 2008 ), possibly by inducing proteolysis of endogenous p21 BAX to produce p18 BAX in SH-SY5Y cells (human neuroblastoma) ( Wongchitrat et al., 2019 ). ZIKV induced neuronal apoptosis by increasing mitochondrial fragments ( Yang et al., 2020 ).…”